linuxaudio.org

On Fri, Oct 17, 2008 at 02:33:00PM -0400, Paul Coccoli wrote:
> There's no chance that a compiler optimization is hiding the bug,

quoted text
> because we haven't turned on optimization.

But there is nothing that stops the compiler from writing

read_ptr any number of times it wants unless you make that

variable volatile.
>  HOWEVER, if you go back

quoted text
> to the original version and REMOVE the volatile qualifiers, then

> re-compile with -O2, NOW a compiler optimization is hiding the bug

> (and the test passes)!  The rb->read_ptr is presumably cached in a

> register and hence only modified once (giving the same affect as the

> patch).

Indeed. The original version really invited the problem,

by *forcing* the compiler to write read_ptr twice.
Ciao,
--

FA
Laboratorio di Acustica ed Elettroacustica

Parma, Italia
Lascia la spina, cogli la rosa.
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